Asphalt emulsion



Patented May 6, 1930 UNITED STATES PATENT: OFFICE PIERCE 11:. TRAVIS, or 'RInGEwoon, AN'D ARTHUR L. HALVORSEN, 0 PERTH AmEoY, NEW JERSEY, ASSIGNORS TO THE. EMULSION rRocEsscoRroRA'rIon, or JERSEY CITY, NEW JERSEY, A CORPORATION or DELAWARE ASPHALT EMULSION No Drawing.

This invention relates to asphalt emulsions and has for its object the provision of certain improvements in the manufacture of asphalt emulsions.

The asphalt emulsions of commerce are for the most part mixtures of asphalt and waterwith various agents designed to effect and maintain an emulsification of asphalt and water. Colloidal clays have been largely used commercially as the emulsifying agent, while various other substances have been suggested in the patent and other literature, such for example as colloidal vegetable and animal substances, soaps, alkalies, etc. In all cases, however, relatively large amounts of emulsifying agent have been prescribed as necessary in order to produce a reasonably stable asphaltand water emulsion.

In the copending application of Hans M. Gasmann, Serial No. 211,006 filed August 5, 1927, the preparation of asphalt-Water emulsions with relatively small amounts of sodium silicate as the emulsifying agent is disclosed. As stated 'in that application, there appears to be a critical relationship between the amount of sodium silicate used and the efiectivene'ss of the emulsification, Whereby satisfactory emulsification can only be attained when the amount of sodium silicate employed is less than 1% by weight on the emulsion. In preparing asphalt-water emulsions by the Gasmann process, we have observed that there is a tendency for the formation of asphalt skins on atmospheric contact surfaces. These skins seem to be occasioned either by, the reformation of asphalt or by the inversion of the asphalt-in-water emulsion to a water-in-asphalt type of emulsiOn at such surfaces of the emulsion as "are in contact with the atmosphere, and consisting, as they do, of substantially free asphalt, they tend to harden and thereby become d1fiicult to reemulsify by mere stirring. 4

We have now discovered that the inclusion in such asphalt-water emulsions of a small amount of fatty acid notably retards the formation of asphalt skins on atmospheric contact surfaces. While for commercial and practical reasons we prefer to use ordinary technical oleic acid, other fatty acids, such Application filed January 10, 1928. Serial No. 245,804.

as stearic acid and palmitic acid, exercise and preferably oleic acid. In our preferred practice the amount of sodium silicate em- Iployed for emulsification is less than 0.75%

y weight on the emulsion and the amount of fatty acid is less than 0.5% by weight on the asphalt in the emulsion. Ordinarily, considerably smaller amounts of the fatty acid will serve the desired purpose, and we have attained excellent results withv as little as- 0.025% by weight of oleic acid on the weight of asphalt employed. In our preferred practice we effect the emulsification with from 0.1% to 0.4% by weight of sodium silicate on the weight of the emulsion and with the addition prior to or during emulsification of about 1 pound of oleic acid for each ton of asphalt employed; that is about 0.05% by weight of oleic acid on the weight of asphalt employed. 7

In carrying out the invention, all of the fatty acid may be added to the hot water containing the sodium silicate, or the fatty acid may be added at intervals during the addition of the molten asphalt to the Water. We have secured satisfactory results by adding about two-thirds of the fatty acid to the hot water containing the sodium silicate, prior to the addition of the molten asphalt, and the remaining one-third of fatt the end of the asphalt feeding period. In other respects, the preparation of the emulsions may be conducted in substantial accordance with the procedure described in the aforementioned Gasmann application.

The addition of small amounts of oleic or other fatty acid prior to or during the addition of the asphalt to the water, as contemplated by our present invention, beneficially promotes the preparation of the emulsion.

acid towards acid appears to act like a lubricant, probably by soap formation, and facilitates the dis semination of the asphalt and its emulsification with the water. Thus, the emulsification of the asphalt and water, particularly with relatively high ratios of asphalt to Water, is

more easily and readily accomplished in the presence of such a small amount of a fatty acid as herein contemplated than when the fatty acid is omitted.

The following example illustrates the practical application of the invention in the preparation of an emulsion having a relatively high ratio of asphalt to water. It is to be understood that this example is merely illustrative and in no sense restrictive of the application of the invention.

250 kilograms of water containing 2 kilo grams of sodium silicate is heated to a temperature of about 80 (1., as for example by the injection of live steam. 0.6 kilograms of oleic acid (0.08% by weight on the asphalt employed is added to the waterprior to the addition thereto of the molten'asphalt. Or,

if desired, about two-thirds of this amount I of the of oleic acid may be added to the water at the start of the emulsifying operation and the remaining one-third added towards the end of the asphalt feeding period. 750 kilograms of molten asphalt at about 135 C. is introduced into the water in a regulated stream and with continuous agitation from a fast moving propeller agitator. The preliminary coarse emulsion formed in this way is now fed, continuously and with appropriate stirring into a mechanical emulsifier such as a colloid mill, from which the finished fine emulsion is continuously discharged. The fine emulsion discharged from the emulsifier is cooled, artificially if desired, with gentle stirring and canned, or otherwise prepared for storage or use.

The cooled emulsion resulting from the foregoing operation is of a dark brown color and of a heavy consistency but will yet flow which is remarkable considering the high asphalt content (3 parts by weight of asphalt to 1 part by weight'of water) and the small amount of emulsifying agent (0.2% by weight on the Weight of the finished emulsion).- -As a consequence of the inclusion small amount of oleic acid (0.08% by weight on the weight of .the

some asphalt skins hard to reemulsify. Furthermore the inclusion of the oleic acid reasphaltic constituents duces the danger of over-feeding the asphalt,

resulting in asphalt accumulation, and hence the asphalt may be added to the water w1th less care to prevent over-feeding and in less time than where the oleic acid is omitted.

The emulsion prepared in accordance with the invention, while Very stable in the cans, reforms true asphalt in a very few minutes when coated on a concrete wall, cardboard, metal, etc.; the coating being just as waterproof, black and shining as when formed from non-emulsified asphalt. trated emulsion may, if desired, be thinned with water to form a more dilute emulsion. For example, 2 parts of t e emulsion prepared in accordance with tie foregoing'ex ample may be mixed with 1 part of water to make a thin brown emulsion of milk-like consistency containing about 50% pure as- I phalt.

While the invention is of general application and can be advantageously practiced with substantially all asphaltic materials, it is particularly applicable in preparing emulsions of asphalt containing relatively small percentages of mineral matter. Thus, for example, natural or residual Bermudez asphalts, or cut-back asphalt cements thereof, containing 1 to 7% mineral matter are admirably suited for the practice of the invention. Similarly, the residual asphalts from the distillation of other asphaltic base oils, or cut-back asphalt cements thereof, are well suited for the practice of the invention. Such asphaltic substances contain a relatively high percentage of constituents soluble in carbon bisulfide. Emulsions made of such asphalts contain relatively small amounts of mineral or similar inert matter, and consequently contain maximum percentages of the desirable hydrocarbon compounds of asphaltic materials. Employing such asphalts in the practice of our invention, the resulting emulsions contain over and preferably not less than by weight of combined water and soluble in carbon bisulfide.

The asphalt emulsions produced in accordance with the invention are freely flowing liquids, as contrasted with the paste-like products of equivalent asphalt content that have heretofore appeared on the market.

These emulsions are, moreover, true emulslons 1n which the asphalt 1s uniformly dis persed in a very fine state of sub-division.

Under a high powered microscope, these emulsions are seen to consist of minute glob ules of asphalt very uniformly distributed throughout the water, which constitutes the continuous or external phase of the emulsion.

Where other agents or substances are add ed to emulsions prepared in accordance with OllP'lDVGllljlOll, care must be taken not'to add substances that exercise a deleterious efiect upon or break d wn the emulsion. For ex- The concen ample, colloidal clays and other colloidal earthy substances are antagonistic in emulsions prepared in accordance with our invention, and the addition of very small amounts of such substances will break down the emulsion. In all cases, however, the additive substances including the emulsifying agent and fatty acid will not exceed a few per cent, say about 2%, by weight on the emulsion and the emulsion will thus consist principally of water and asphalt.

We claim 1. The improvement in the manufacture of asphalt-water emulsions which comprises ef: footing the emulsification of the asphalt and water with sodium silicate in amount not exceeding 1% by weight on the emulsion and in the presence of a fatty acid in amount not exceeding 0.5% by weight on the asphalt em I ployed.

2. The improvement in the manufacture of asphalt-water emulsions which comprises adding molten asphalt to a body of actively agitated hot water containing sodium silicate in amount not exceeding 0.75% by weight on the resulting final emulsion and fatty acid in amount not exceeding 0.5% by weight on I the asphalt employed.

3. The improvement in the manufacture of asphalt-water emulsions which comprises effecting the emulsification of the asphalt and water with a small fraction of one percent of sodium silicate and in the presence of fatty acid in amount not exceeding 0.05% by weight on the asphalt employed.

4. The improvement in the manufacture of asphalt-water emulsions which comprises gradually adding molten asphalt to a body of actively agitated hot water containing 0.1 to 0.4% by weight of sodium silicate on the resulting final emulsion, and effecting the emulsification of the asphalt and water in the presence of fatty acid in amount not exceeding 0.5% by weight on the asphalt employed.

5. The improvement in the manufacture of asphalt-water emulsions which comprises efiecting the emulsification of the asphalt and water with about 0.1 to 0.4% by weight of sodium silicate on the emulsion and in the presence of fatty acid in amount not exceeding 0.5% by weight on the asphalt employed.

In testimony whereof we afiix our signatures. I

PIERCE M. TRAVIS. ARTHUR L. HALVORSEN. 

